DESCRIPTION: The overall objectives are to relate the optical properties of normal, diseased and damaged corneas to their structures. The optical properties including transparency (or light scattering), haze, and polarized light scattering and propagation, and the structures include fibrillar and lamellar organization and keratocytes. The Specific Aims are: 1) to elucidate structural bases for diffuse haze seen in edematous, and certain diseased and damaged corneas; 2) to use light scattering in fresh corneas to test different electron micrograph (EM) preparative procedures; 3) to evaluate the importance of specular and non-specular scattering from keratocytes; 4) to relate birefringence and small angle polarized light scattering in normal and diseased corneas to their lamellar and fibrillar structures; and 5) to correlate visual performance with objective measurements of haze following laser photokeratectomy. The general approach involves a strong interplay among theory, light scattering experiments, histology, and clinical techniques. Theoretical light scattering can indicate light scattering measurements that can be made or fresh tissue and test the validity of structural features depicted in EM. Understanding the structural bases for light, scattering in abnormal corneas has obvious health implications. Moreover, light scattering techniques have the potential of providing a non-invasive probe of characteristics of the structures responsible for the optical properties and structural integrity of cornea. The alterations of lamellae ultrastructures in keratoconus suggested by x-ray measurements should be detectable by birefringence measurements which can be made in vivo. Finally, the scatterometer can be used with clinical colleagues, to correlate degradation of visual function with the corneal haze that follows excimer laser keratectomy and assess the clinical significance of haze. The theoretical and experimental light scattering techniques will include transmissivity and angular scattering methods developed by this team, and confocal microscopy. The theoretical scattering analysis analyses will be based on the ultrastructures in EM an on cell models. All the scattering measurements will be made on fresh tissues, and comparisons with predictions test the validity of the structures shown in EM. Birefringence measurements will be combined with theoretical and numerical analyses to be developed by this team. Comparisons will be made between scatterometer and visual function measurements on patients.